Pref-1 (Preadipocyte factor-1) is expressed in adipose precursor cells, downregulated during differentiation and is absent in mature adipocytes. Thus, Pref-1 is widely used as a preadipocyte marker. We have shown Pref-1 Inhibition of adipogenesis by gain- and loss- of function studies in vitro as well as in vivo. Pref-1 is synthesized as a plasma membrane glycoprotein with 6 EGF-repeats in its extracellular domain; the Pref-1 ectodomain is cleaved by TACE at the juxtamembrane region to generate the biologically active soluble Pref-1. Pref-1 inhibits adipocyte differentiation by activating MEK/ERK and we recently detected an interaction of Pref-1 with fibronectin. The goal of this research is to further elucidate the molecular mechanisms underlying the Pref-1 function in adipose tissue development. First, we will examine the Pref-1 interaction with fibronectin and the specific integrin receptor that mediates Pref-1 inhibition of adipocyte differentiation. We will also study the fibronectin/integrin signaling pathway that is dependent on the Pref-1/fibronectin interaction in inhibiting adipocyte differentiation. Downstream signaling molecules including FAK and Rac will be examined. Next, to mark and characterize Pref-1 expressing adipose precursor cells, we will generate Pref-1- reporter mice that express GFP and RFP in an inducible manner. Using these reporter mice, we will monitor and examine Pref-1 expressing adipose precursor cells. We will also define the signature of these cells by genome-wide microarray analysis. Furthermore, comparison of the expression patterns as affected by Pref-1 null and Pref- 1 overexpression will help us to understand the Pref-1 function in adipose precursor cells. PUBLIC HEALTH RELEVANCE: Obesity is a major health problem causing metabolic syndrome and type II diabetes, and the control of adiposity is a top priority in managing these diseases. This research is directed toward understanding adipocyte differentiation and adipose tissue development, the process that contributes to the development of obesity. Elucidating the mechanisms of Pref-1 function and regulation will allow us to begin to develop strategies to control obesity.